Main noise influence of the RIN laser diode of an EML transmitter used in an UWB RoF link

The use of precise large signal models for optoelectronic devices, such as laser diode, electro-absorption modulator, optical fiber and photodiode, is useful to simulate and to predict the performances of an optical fiber link. Moreover, to characterize its dynamic range and this last influence on a high data rate digital signal, it is necessary to develop not only nonlinear models, but also noisy models taking into account both electrical and optical operating of the devices. This paper presents the simulation results of an optical fiber link on which the optical signal is externally modulated by an UWB OFDM signal. Simulations are performed using co-simulation on ADS system simulator Ptolemy. The envelope simulator is used at the circuit level thanks to the developed large signal electrical models of the E/O and O/E devices. These simulations highlight the greater influence of the RIN of the laser diode, compared to the other additive noise sources on the optical link. In some cases, this influence could affect significantly the RoF system performances, particularly in case of a low-level input power UWB signal and of UWB multi-channels use.